Dry kiln and the art of kiln drying



Aug. 7, 1928.

J. F. COBB DRY KILN AND THE ART OF KILN DRYING Filed Sept. 16, 1926 2Sheets-Sheet J. For/esf- 0,62).

Aug. 7, 192s. 1.680.013

J. F. COBB DRY KILN AND THE ART OF KILN DRYING Filed Sept. 16, 1926 2Sheets-Sheet 2 J lib/wwf Cobb- Patented Aug. 7, 1928.4

UNITED STATES 1,680,013 PATENT OFFICE.

J. FoRaEsT CORR, OF PORTLAND, OREGON, AssIoNOR To MOORE DRY xiLNCOMPANY, JACKSONVILLE, FLORIDA, A CORPORATION OR FLORLOA.

DRY KILN AND THE ART QF XILN DBYING.

Applicaties ined sepmber is, 192e. semi No. 135,891.

My invention relates to the art of kiln drying and to dry kilns of thetype in which circulation of the atmosphere of a kiln is effected by therotation of a series of powerdriven rotary fans operably mounted withinthe kiln.

The main Object of my invention is-to provide a circulation within akiln of the entire volume of the gaseous contents of the kiln,

l0 as a whole, wherein the volume of gas on one side ofthe drying stockis drawn through the interstices in the stock'to the other side thereof,and thence back again to the side lirst named in constant circulation.

In the said course of circulation the gas is kept properly humidifiedand raritied to effect the best dryin results. A

' Another object o my invention is to provide in a kiln novel means foroperatively mounting the fans aforesaid, wherein the result of anexceedingl stable and durable kiln structure is arrived7 at, with dueregard to economy, and whereb the functional efficienc of the kiln, bothin regard to the uniy formity of the drying operation, its reo'ulationand control, is materially enhanced? What constitutes my invention willbe hereinafter specified in detail and succinctly defined in theappended claims..

In the accompanying drawings, -wherein my invention is illustrated inpresent preferred form of embodiment, i

vFigure I is a partial round planof one of my kilns taken in al aneabove, the lioor w ich forms the top o the fan-duct thereof, the middleportion of the kiln being broken away in order to accommodate thedesired scale of the drawing, andthe floor aforesaid being broken awayat its opposite ends in order to expose to view the heatingv coils thatI are disposed'below it.

Figure II is a' longitudinal vertical section of the subject matterof.Figui-e I as shown therein, and showing also the details, includingthe superstructure, of the kiln.

i Figure III is a transverse vertical section taken on the line III--IIIof Figure II.

Referring to the numerals on the drawings, l'indicate's the bottom, 2and 3 the opposite side walls, and 4f the roof of a l {i1n which ismade, preferably throughout, of concrete construction, the bottom beinmade suiciently heavy and of a properdistribution of its thickness tosupport the distribu- 55 tion of the weight it has l2? arry.

.walls 9 The roof 4 is provided at suitable intervals withdamper-controlled ventilators 5, disposed in two series along theopposite sides of the roof. The opposite end openings in the kilnchamber located above the end walls 6 and 7 of the base of the kiln areclosed, during the operation of the'kiln, b respective doors 8, whichmay be, in' eac instance, of any preferred type that is suitable for thepurpose.

A distinctive feature of my present invention is to be found in thefan-duct of the apparatus which comprises a continuous vertical wallextending substantially from end to end of the kiln, and preferably inthe lower part of the kiln, in a zigzag direction, substantially asshown in plan view in Figure I. The zigzag effect of said wall isachieved by dividing the length of the kiln into medial compartments, ofsubstantially uniform and preferred dimensions, by a series ofalternately disposed substantially parallel artition walls 9 and 10,each of the eing solid, and each of the walls 10 being provided with anaperture of suitable dimensions to accommodate within it one of a seriesof rotary fans 11. Each air of next adjacent walls 9 and 10 is unite onone side b a solidvertica'l wall 12, constituting in e ect a closure onone side for the compartment to which it is appropriated, the side ofthe'compartment opposite each wall 12 being open.

The walls 12 are disposed, res ectivel in succession on alternate sidesof t e fanuct, so as to divide the series of compartments into units Ofwhich each alternate one is open on one side and closed on the otherside. The result of the disposition just described of the several walls9, 10 and 12,is.to impart, in their assemblage,to the length of theentire Vwall so constitutedthe `zigzag diiiction already designated.

The angle at which the walls 9`-and 1() meet the walls 12, res ctively,is shown in the drawings as a rig t angle; and that is at present deemedto be the preferable angle, but it is obvious that the angle may bevaried if desired,4 as in some instanceslit may be.

Each of the walls last named is planted firml on theV bottom 1 of thekiln, with whic in the concrete construction preferred, it isincorporated. The faii-duct is coin leted by a floor 14 which is laid,with airtight closure, 0n the top 0f tbe'wells 9, 10 and 12,.

The door 14 is preferably rovided on opposite sides with upstan inglateral flanges 15, which, when made of concrete, is incorporated withthe said floor and walls in a unitary concrete construction. The floor14 is reinforced and supfported at required intervals by cross gir ers16, preferably I beams, whose opposite ends are let into and supportedby the side walls 2 and 3, respectively, of the kiln.

The floor 14 carries track rails 17, and is for that reason preferablybut not necessarily, particularly if but one end door is used, inclinedslightly towards the outlet door 8 of the kiln, in order to utilize theforce of gravity to facilitate propulsion along the track `to the pointof exit of trucks 18, when they are loaded with stock to be dried in thekiln. The height and width of the two corridors 19 and 20 that aredefined on the outside of the 4fan-duct by the side walls 2 and 3 andthe floor 14, respectively, should be sufficient to accommodate workmenwithin them -with space for freedom of actionA as occasion may re uire,it being taken into account that sai corridors are provided,respectively, with substantially longitudinally coextensive fresh airducts 21 and 22 through lateral apertures 23 in which rovision' is madefor admission in reguated quantity, of a su ply of fresh, atmosphericair as often as esired, the said fresh air ducts being supplied withoutside air through terminal, door-controlled, air intake openin 24.

Below the level of the bottom of the floor 14, in the respectivecorridors 19 and 20, are disposed heating means, preferably coils ofpipe 25 and 26, arranged in any suitable and preferred system'fordistribution of heat, preferably steam heat that may be derived from anypreferred source of steam supply, not illustrated.

A variety of steam and other heating systems being well known,in theart, it is deemed unnecessary to specify more in detail theparticular'systern illustrated,.inas much as it constitutes, in itself,no part of my present invention.

The complement of fans 11 is driven preferably by a single shaft 27carried in suitable aligned bearings in upright 'supports 28 'erected ontheV bottom 1' of the kiln. The shaft 27extends' through the successionof walls 9 and 10 and preferably to the outside of the end wall 6, whereit 'is operatively connected, as byY a flexible coupling 29, to a motor,for example an electric motor 30, preferably located, with otherincidental elements unnecessary to specify, in a housing chamber 31.

The shaft 2( may be driven in'one direction only, or if provided, as itmay be, with suitable reversible fans, its direction of rotation may bereversed at will, with the cffect, in reversal, of the direction ofcirculation of the atmosphere of the kiln.

I prefer to provide each one of the series of compartments, defined,respectively, by the zigzag wall above described, with a sidewingdetlecting baffle 32 (compare Figures I and III), whereby uniformdirection is imparted to the currents of the circulatory medium in thekiln.

The baiiles 32 are preferably located substantially in the middle ofeach compart- -ment, and are, respectively, of a length equal to onehalf of the width of the compartmeiit. Bytheir disposition, the bailleis caused, in effect, to split, with increase of its efficiency, thecurrentof the circulatory medium as discharged from each compartment.The outside wing 33 of each baille 32 is, in effect, hinged to thebaille for control of the direction of movement, preferably by apermanent flexure, whereby the angle of each wing may be convenientlyadjusted if required by application of force sufficient to bend themetal of which it issconstituted.

The stock 34 to be dried in the kiln, when of lumber, is loaded in astack or stacks upon such number of trucks 18 as may be requisite, andthe method of stack piling may be of the horizontal order or of anyother that may be referred.- In the drawings the stock is il ustrated ashorizontally pi ed, and in such case a fin 35, depending towards thestock pile from the middle of the roof 4 may be employed to advantagefor compelling the kiln'atmosphere under pressure to circulate throughthe horizontal spaces between the stock in the pile instead of over thetop ,of the stack.

It is proper to add, that it is deemed unnecessary to specify alldetails of the heating system, besides means common in the art forautomatically humidifying and ventilating the atmosphere of the kiln,but that variation of said details at will are contemlated as comingwithin the scope of my invention.

At intervals within the kiln, Iprefer to provide spray pipes 36, whichmay be made at will to discharge a spray as of steam, air, or even waterinto the atmosphplie of the kiln for the pur se offproper y' uniidifyingit. lA hu'mi ity-control box 37, of any well known or suitable typepreferred,

located in the housing chamber 31, may be used if desired.

Each of the two series of ventilators is' o ened at a time on one sideonly. of the kiln, their purpose being to lead off spent or used dryingmedium as it accumulates in the operation of the Discharge from the openventilators of a'series is made from the side of the kiln which isopposite tothe discharge side of the fan-duct.

Fresh air through the ducts 21 or 22 is introduced only on the suctionside of the fan system, which, it should be observed is, in view of thepotential reversibility of the direction of rotation of the fans, a tcrmof dual significance.

A description of the operation of my kiln, including specification ofcertain features of my invention, in so far as it pertains to the art ofkiln drying, follows in immediate sequence.

Assuming a kiln to be built along lines in substantial conformity tothose illustrated in the drawings and to be equipped with opera: tivemechanism substantially equivalent to that illustrated, if it be assumedthat the kiln is supplied with material to be dried. represented by thetruck load 34, that the doors (or door) 8 are closed.- and that thecoils 25 and 26 are heated, the drying operation is ready to start.

Thereupon the motor 30 is set in motion which is communicated to thefans 11 as by aid of the shaft 27.

Each fan, as has been specified, operates upon the gaseous contents oftwo contiguous compartments, upon one compartment with suction effectand upon the other with pressure effect. v

Bearing in mind that the direction or rotation of the fans isreversible, and that consequently one compartment may be at one time thesuction side of.the fan. and that upon reversal of movement of the fan,it will be converted to the pressure side thereof, it will be understoodthat all the fans operate in unison to effect a substantial uniformityof suction on one side of the interior of the kiln, and to exert acorrespondingr pneumatic pressure on the other side of the kiln.

Wherefore, one side of the kiln while in operation is denominated thesuction side. and the opposite side the pressure side of the kiln. Theapplicability of the names just indicated depends, as has just beenpointed out, upon the direction of rotation of the complement of fans.The pneumatic pressure generated bv the fans may be by the baffle wings33, directed towardsl one end or both ends of the kiln -with the effectof producing circulation of the atmosphere of the kiln`bothlongitudinally and transversely in respect to the interior of the kiln,in order to satisfy the demands of the kiln conditions.

By reason of the presence of the depending fn 35 above the stock loadand of the lateral flanges 15 of the floor 14 below the same on theoutside of the wheels of the trucks 18, the result of the coactingsuction and pressure forces s.lby their push and pull coaction, forciblyto drive the circulatory medium with quick, powerful and uniform dryingeffect through the interstices provided for circulation through the pileof stock 34.

An important feature of my invention is the method by which each fanunit is provided with one inlet and one outlet of circulatory medium foreach fan in whichever direction the fan revolves. It is bymultiplication of said fan units that the result in kiln ldrying isachieved of utilizing a unified drying current, with material increasein efficiency form a volume of air standpoint.

In regard to operation of the ventilators in two series, it should beconsidered that in the operation of any drying kiln the circula-A torymedium soon becomes heavily charged with the liquid constituents of thedrying material. The excess moisture so derived must be properly drawnoft' in order to maintain the efficiency of the apparatus. By providingtwo series of ventilators 5 and operating only one series at a time, theexcess of moisture aforesaid may be kept properly drawn off. The freshair ducts 21 and 22 contribute to the same end by substituting for thespent atmosphere of the. kiln that is drawn off, fresh outside air ofsuperior drying quality. The correctness of the rinciple upon which theventilators and resh air ducts operate, respectively; is well recognizedin the art. but the successful application of that principle is promotedby my invention, whereby provision is made on one'side ofthe kiln fordrawing off the spent atmosphere immediately after it has passedthroughthe drying stock and becomes thereby sureharged with moisture,and then supplying fresh air from the fresh air duct which is located onthe same side of the kiln as the active series of ventilators islocated, it being understood, of course, that when the fresh air duct 21is open, the duct 22 is closed, and contrariwise. When the duct 21 isopen, the series. of v'entilators on the same side of the kiln as theduct 2l is open and the ventilators of the series' on that side on whichthe duct 22 is located are closed as well as the duct.

Provision of two fresh air ducts and two corresponding series ofventilators is made in order to effect the practical reversibility ofthe fans, already specified.

In the operations which have been descrbed of drawing off the spentatmosphere of the kiln and the introduction of fresh air in place of it,it is impracticable to measure those operations with' any degree ofexactitude. For that reason` in part, I employ the spray pipes 36 whosefunction is to provide means for maintaining the humidity of the kilnatmosphere substantially at normal.

Another resultant advantage of method of circulation accomplished by myinvention is that the vcirulatory medium in each complete circuit is, indescending and in ascending currents, respectively, twice passed throughthe two heatingcoils that are disposed, respectively, on opposite sidesof the kiln.

The advantage afforded by my lnyention the circulation in the kiln iscontributory, and

under some conditions may be necessary.

What I claim is: A

1. A dry kiln compri-sing within it a`fanduct defined, in part, by acontinuous substantially vertical wall extending substantially the fulllength of the kiln in a zigzag direction.

2. A dry kiln comprising within it a fanduct defined, in part, by acontinuous substantially vertical wall extending .substantially the fulllength of the kiln in a zigzag direction, said wall including aseries ofalternately disposed partition walls', of which each alternate one issolid and each alternate one is providedwith an aperture foraccoinmodationwithin it of a fan.

3. A dry kiln comprisinv a bottom, avertical fan-duct defining wall, anda floor laid` on said wall, all being ofvunitary concrete. construction,saidA wall being composed of alternately disposed solid and a ertured vpartitions united on one side thereo respectively, to solid wallsdisposed successively on opposite sides of the duct, whereby a zig-v zagdirection is `imparted to the. fan-duct defining wall as a whole.

4. The combi-nation with the outside walls of a kiln of a zigzagfan-duct defining a wall extendingV substantially the full length of thekiln and'comprising alternately disposed solid and apertured partitionwalls, respectively of rotating fans operatively mounted in theapertiired partition walls, respectively,

` and driving means in operative communication with the respective fans.A

5. A dry kiln comprzsingwithin it a fanduct defined, in part, by acontinuousl submuy the wall extending substanf-ull length of the kiln ina zigzag said wall including a. sei-ies of alternately disposedpartition walls, -of which each alternateone is solid and each alternateone isv provided with an aperture for accommodation within it of a. fan,said fan-duct being located in the lower art of the kiln, 4a floor abovethe fan-duct, eating means locatedon opposite sides of a respectively,adjacent to the `said floor, whereby circulatiomof the circulatorymestantially vertic direction,

kiln, j

dium of the kiln produced by rotation of the fans is caused, in passingfrom one side to the other of the kiln, to pass twice through saidrespective heating means.

6. In a dry kiln, asubstantially vertical wall extending longitudinallyof said kiln and having a pluralit of substantially transverse partitionwals, alternate partition walls having an opening, a common drive shaftextending longitudinally through allof said partition walls, andapliirality of fans mounted upon said shaft and disposed in the openingsof alternate partition walls.

7. The combination with a'dry kiln, of a fan unit consisting of avertical wall extending substantially longitudinally of the kiln,substantially transverse walls associatedtherewith and providing a pairofcommunieating compartments opening toward opposite sides of the kiln,and means inducing circulation of air from one compartment to the other,one of said compartments constituting an inlet on one side of said meansand thc other compartment constituting an outlet on the other side ofsaid means.

8. The combination with a dry kiln, a 90 yertical wa'll arrangedcentrally and extend-1 ing substant: ally longitudinally of the kiln,"transverse partition walls extended from o posite sides of said verticalwall to provi e a pair of compartments opening toward oppos'te sides ofthe kiln, means o communica.-l tion between said compartments, andreversible means associated with said means ef communication forinducing circulation of` air fromv one compartment to the other. 1"

9. The combination with a dry kiln, of a "fan unit consisting of avertical wall extending substantially'longitudinally of the kiln, sustantially transverse walls associated therewith and providing a pairofcommunieating compartments opening toward opposite sides 'of the kiln,and means inducing circulation of air from one compartment to the other,one ofsaid compartments constituting an inlet on one side of said meansand the other compartment constituting an out-A let on the other'side ofsaid means, and a vertical baille arranged substantially transversely ineaicli compartment and terminating adjacent the middle thereof. n

10. The combination with a dry kilrg" of a fan unit consisting of.communicating compartments and an intermediate rotary fan, one of saidcompartments 4constituting an inlet on one side of the fan andthe othercompartment an outlet on the other s'zde of' the fan, and a baillearranged intermediate each com the midd e thereof.

In testimony whereof, I have hereunto set my hand.

J. FORREST COBB.

artment and terminating adjacent Y

